The disclosures herein relate generally to portable computer hard disc drives and more particularly to an impact shock absorbing mounting apparatus and method for such hard drives.
Hard disc drives (HDD's) are one of the most common sources of field failures in computers. Within an HDD housing are several thin glass discs, i.e., magnetic media, each having an associated flying head. Thus, HDD's are one of the most fragile components of the computer in terms of sensitivity to impact. This is particularly true in cases where a major component of the impact forces is normal to the surface of the hard drive media. HDD's are more sensitive in this orientation because there is opportunity for read heads to come into physical contact with, and cause damage to the discs.
Upon impact, the heads bounce and contact the discs. The discs may be either broken or scored by such impact. Loose particles may also result from such impact and become free to move around inside the HDD cassette and contact other parts of the drive thus causing new failures. Furthermore, such impacts cause shock to the entire HDD cassette, not just to the heads.
Attempts to cushion the drives against shock from impact have produced elastomer feet on the bottom or rest surface for providing a cushioning effect of the portable computer housing on its associated support surface. These feet also serve as friction surfaces to limit lateral movement of the portable computer relative to its support surface. Cushioned mounts placed within the computer housing provide vibration damping but have not addressed the issue of where such mounts should be located to provide maximum protection from impact shocks. This is an important oversight because protection from the forces from impact shocks require an entirely different solution than protection from vibration.
When portable chassis are manufactured, a hard disc drive (HDD) bay is provided to accommodate larger HDD's, for example an 8 gig HDD having a thickness dimension of about 12.7 mm. Therefore when an HDD of that size is placed in the bay, there is little extra room left for the HDD to move upon impact shock because there is adequate mechanical support for the HDD. However, sometimes a smaller capacity HDD is provided, for example such as a 2-4 gig HDD having a thickness dimension of about 9.5 mm and inherently having less structural rigidity. When this occurs, there is an available 3.2 mm. of space which provides no mechanical support for the smaller thickness HDD. As a result, this leads to HDD failures when the system chassis is subjected to shock in the Z direction. This is particularly a problem when the head is away from the parked region, such as when the HDD is reading, writing or seeking, because these are the more fragile states of an HDD. During such unpact shock loads, the HDD chassis flexes away from the bottom or support surface of the system chassis and then returns to impact the support surface. This violent flexing and impact occur within a period of less than 2 ms, and is the single most damaging action to an HDD.
In U.S. Pat. No. 5,673,171, a mounting plate, representatively of a metal construction, is spaced apart from the support tray member top side portion in an overlying, parallel, facing relationship therewith, the mounting plate having a top side and a rear end portion. Fastening means are provided for securing the mounting plate to the support tray member top side portion. Additionally, resilient means are captively retained between the mounting plate and the support tray member top side portion and project downwardly beyond the support tray member to provide for handling shock absorption for a disc drive secured atop the mounting plate when the tray/plate assembly is, for example, placed on a support surface outside of the housing cage structure. Securing means are also provided and function to removably secure a disc drive to the top side of the mounting plate.
Therefore, what is needed is a method and apparatus for providing cushioned impact shock protection for smaller HDD's mounted in larger HDD bays in portable computers, which protection is strategically located to substantially reduce damage from impact forces acting normal to the bottom surface of the portable computer housing.